- This artical is about the hydroxyl functional group. For the Hydroxyl radical see Hydroxyl radical.
Hydroxyl in chemistry stands for a molecule consisting of an oxygen atom and a hydrogen atom connected by a covalent bond. The neutral form is a hydroxyl radical and the hydroxyl anion is called a hydroxide. When the oxygen atom is linked to a larger molecule the hydroxyl group is a functional group (HO– or –OH) .
The term hydroxyl group is used to describe the functional group –OH when it is a substituent in an organic compound. Organic molecules containing a hydroxyl group are known as alcohols (the simplest of which have the formula CnH2n+1–OH).
The hydroxyl radical, ·OH, is the neutral form of the hydroxide ion. Hydroxyl radicals are highly reactive and, as a consequence, short-lived; however, they form an important part of radical chemistry.